1. Field of the Invention
The present invention relates to an image processing method and apparatus for correcting the unevenness of density in an image formed by using a plurality of recording elements, and a recording medium.
2. Related Background Art
An ink-jet printer which has hitherto realized the high quality of printing has a plurality of colors of ink mounted thereon. This ink-jet printer has been designed to achieve its high quality by performing a printing operation using a special color in addition to four basic colors. Further, since an image is configurated by dots in the printer of an ink jet type, when dots discharged from some nozzles are smaller than other dots, rasters formed by these nozzles constitute an image thinner than other images. On the contrary, when the dots discharged from the nozzles are larger than other dots, an image which is deeper than other images is formed. Therefore, for instance, when an even density image is printed by a head, the unevenness of density is generated in the main scanning direction of the head. The unevenness of density is corrected by adjusting the number of dots. The ink-jet printer on which a plurality of colors of ink are mounted is designed to print a print pattern for each ink and to read the print pattern by a printed matter reading device in order to correct the unevenness of density in printing and maintain the quality of an image. When the correction amount is calculated from the read image, the full color data of RGB of the read image is converted into gray scale data to detect the unevenness of density. Thus, it is decided whether the read image is thinner or deeper on the basis of a fact that the gray scale data is larger or smaller than a reference. A correction table is prepared in which a correction amount is obtained by multiplying the difference between the reference and actual gray scale data by a certain constant, and the gradation of the print pattern is determined as an input for each color of ink, and the correction amount is added to the gradation as an output. Thus, multi-value image data is converted into multi-value image data and the multi-value image data thus obtained is binarized to adjust the number of dots, and thereby the unevenness of density is corrected.
However, in the above mentioned conventional example, in case of a color which reacts only to a B filter, for example, yellow ink or the like, if the full color data of RGB is converted into gray scale data, it may be possibly converted into generally small data and the quantization thereof may become undesirably rough. Consequently, the steps of available correction amount may be also roughened so that the fine adjustment of the correction of density cannot be done. Furthermore, when orange or the like was employed as a special color other than four basic colors, the correction of density could not be properly carried out.
Besides, in the conventional printer of an ink-jet type, nozzles have been provided for actually discharging ink and a head which has been most heavily consumed has been separated from a device so that it can be replaced by another one, and therefore, maintenance has been easy to lengthen the life of the device.
In the above mentioned conventional example, however, there has been generated the unevenness in the diameter of dot of ink discharged depending on heads, hence density difference has been disadvantageously generated depending on the heads. More specifically, when the head is replaced by a new head, there is a difference in density between an image printed by the former and an image printed by the latter. Therefore, it has been impossible to print the same printed matter regardless of printing by using the same image data.
The present invention was devised by considering the above described problems and accordingly, it is an object of the present invention to prevent the density difference between formed images which is generated due to the change of a recording part or the difference in the solid of the recording part by forming processing conditions using a standard value corresponding to the kind of a recording agent.
That is to say, it is an object of the present invention to record an image conscientiously devoted to an inputted image.
In order to attain the above described object, according to a preferred embodiment of the present invention, there is provided an image processing apparatus comprising: an image forming part for forming an image by discharging liquid ink from a plurality of recording elements; a processing unit for processing image data in accordance with a processing condition corresponding to the recording elements; and a generating unit for inputting read data obtained by reading the images formed by the image forming part and generating the processing conditions by comparing the read data with a standard value preset depending on the kind of recording agents.
It is another object of the present invention to form highly accurate correction data by preparing processing conditions with the characteristic of an image reading part used upon preparation of the processing conditions taken into consideration.
In order to attain the above described object, according to a preferred embodiment of the present invention, there is provided an image processing apparatus comprising: an image reading part for reading images to produce image data; an image forming part for forming an image by discharging liquid ink from a plurality of recording elements; a processing unit for processing input image data in accordance with processing conditions suitable for the recording elements; a preparing unit for comparing read data obtained by reading a reference pattern using the image reading part with reference data indicating the reference pattern to create the correction data of the image reading part; and a forming unit for correcting read data obtained by reading the images formed by the image forming part using the correction data of the image reading part and comparing the corrected data with standard values previously set in accordance with the kinds of recording agents so as to form the processing conditions.
It is still another object of the present invention to form highly accurate correction data by preparing the correction data using a standard value corresponding to the kind of a recording agent for printing a pattern. For attaining the above described object, there is provided an image processing method for reading patterns printed by the use of a plurality of recording agents by a reading part and creating correction data corresponding to each of the recording agents, the method comprising the step of producing the correction data using color components relevant to the kinds of the recording agents with which the patterns are printed among a plurality of color components produced in the reading part.
Still other objects of the present invention, and the advantages thereof, will become fully apparent from the following detailed description of the embodiments.